The invention disclosed in Japanese Unexamined Patent Application Publication No. Sho 62(1987)-50136 relates to a plate making method of thermosensitive stencil base paper formed by pasting a porous support member capable of ink copying to a thermoplastic synthetic resin film. According to the plate making method, a conductive layer is provided on a surface of the thermoplastic synthetic resin film of the thermosensitive stencil base paper, a photosensitive layer having photoconductive properties is further provided thereon, and a black toner layer is formed on the photosensitive layer by an electrophotographic system. A toner image is heated by irradiating flash of a xenon lamp including infrared rays to melt and perforate the film of a part corresponding to the toner image, and a plate making image is formed. According to the invention, unlike a method in which infrared rays are irradiated while closely attaching a document to a film, it is not necessary to closely attach the document to the film. Thus, a material other than the sheet document can be printed, and the resolution is increased as compared to a case of perforating while closely attaching the document to the film because the toner image is formed on the film without contaminating the document.